Ballistic panel

ABSTRACT

A ballistic laminate structure in sheet form, which includes a first array of high performance, unidirectionally-oriented fiber bundles and a second array of high performance, unidirectionally-oriented fiber bundles cross-plied at an angle with respect to the first array of fiber bundles, and laminated to the first array of fiber bundles in the absence of adhesives or bonding agents. First and second thermoplastic films are bonded to outer surfaces of the laminated first and second arrays of unidirectional fiber bundles without penetration of the films into fiber bundles or through the laminate from one side to the other.

This application is a divisional of application Ser. No. 08/243,976,filed on May 17, 1994.

TECHNICAL FIELD AND BACKGROUND OF THE INVENTION

This invention relates to a ballistic laminate structure in sheet form,a ballistic panel constructed of a plurality of the sheets, a ballisticgarment constructed of one or more of the ballistic panels, and a methodof fabricating a ballistic laminate structure.

Numerous ballistic laminates are known, for example, those disclosed inU.S. Pat. Nos. 4,916,000, 4,079,161, 4,309,487, and 4,213,812. Prior artlaminates have been constructed of numerous fibers, includingpolyethylene, polyolefin and aramid fibers. Many such prior artlaminates are woven of various fibers, such as aramid fibers sold underthe trademark "Kevlar".

A ballistic non-woven laminate referred to by the trademarkSpectra-Shield is manufactured by Allied-Signal, Inc. The laminatestructure is used in soft body armor to protect the wearer againsthigh-velocity bullets and fragments. Spectra-Shield is made by firstforming a non-woven unidirectional tape, composed of unidirectionalpolyethylene fibers and an elastic resin material that holds the fiberstogether. The resin penetrates to the filament level, impregnating theentire structure with the resin product. Two layers, or arrays, of theunidirectional tape are then laminated together (cross-plied) at rightangles to form a panel. Then, the panel is covered on both sides with athin film of polyethylene on the order of 0.001 inches thick. The filmprevents adjacent panels from sticking together when the panels arelayered together in the soft body armor.

The present invention relates to an improved non-woven ballisticlaminate structure. Enhanced anti-ballistic characteristics are obtainedwhile optimizing use of materials in the laminate. Specifically, it hasbeen determined that ballistic laminates can be constructed of highperformance fibers without using resins to hold the fibers together.This substantially reduces the weight of the structure withoutcompromising the anti-ballistic characteristics of the structure. Asused in this application, the term "high performance fiber" refers tofibers having a tensile strength greater than 7 grams per denier.

By omitting the resin, the cross-plied arrays of fibers directly contacteach other, instead of being encapsulated and therefore separated fromeach other by the resin. An ultra-thin film is used both to cover thecross-plied arrays and to hold the arrays to each other.

The prior art teaches that a critical limit of 80% fiber must bemaintained in the laminate in order to maintain product integrity. Ifthe percentage of resin, covers and the like exceeds 20%, theanti-ballistic qualities of the laminate begin to degrade.

This invention incorporates certain features heretofore recognized asbeing only applicable to older, low performance fibers into the field ofhigh performance fibers in order to achieve a ballistic laminatestructure with enhanced anti-ballistic characteristics.

SUMMARY OF THE INVENTION

Therefore, it is an object of the invention to provide a ballisticlaminate structure in sheet form, which includes a first array of highperformance, unidirectionally-oriented fiber bundles and a second arrayof high performance, unidirectionally-oriented fiber bundles cross-pliedat an angle with respect to the first array of fiber bundles, andlaminated to the first array of fiber bundles in the absence ofadhesives or bonding agents. First and second thermoplastic films arebonded to outer surfaces of the laminated first and second arrays ofunidirectional fiber bundles without penetration of the films into fiberbundles or through the laminate from one side to the other.

According to one preferred embodiment of the invention, thehigh-performance fiber is chosen from the group consisting of aramidfiber, ultra high molecular weight polyethylene, high molecular weightpolyethylene, high modulus vinylon, and liquid crystal polymer-basedfiber.

According to another preferred embodiment of the invention, the firstarray of fiber bundles is cross-plied at an angle of 90 degrees to thesecond array of fiber bundles.

According to yet another preferred embodiment of the invention, thefirst and second thermoplastic films comprise polyethylene film having athickness of 0.35 mils.

According to yet another preferred embodiment of the invention, thepercentage by weight of the high performance fibers in the ballisticlaminate structure is at least 80 percent of the total weight of theballistic laminate structure.

According to yet another preferred embodiment of the invention, aballistic laminate structure is provided, and includes a first array ofhigh performance, unidirectionally-oriented aramid fiber bundles and asecond array of high performance, unidirectionally-oriented aramid fiberbundles cross-plied at right angles with respect to the first array offiber bundles, and laminated to the first array of fiber bundles in theabsence of adhesives or bonding agents. First and second polyethylenefilms, each film having a thickness of 0.35 mils, are bonded to theouter surfaces of the laminated first and second arrays ofunidirectional fibers without penetration of the films into fiberbundles or through the laminate from one sheet of fibers to the other.

According to yet another preferred embodiment of the invention, each ofthe aramid fiber arrays has 10 bundles per inch of 840 denier, 1.5denier per filament fiber.

A ballistic panel is constructed of ballistic laminate structuresaccording to the invention. A panel for preventing penetration of handgun rounds contains at least 10 sheets of the ballistic laminatestructure.

A ballistic panel for preventing penetration of high velocity riflerounds contains at least 40 sheets of the ballistic laminate structure.

According to yet another preferred embodiment of the invention, theballistic panel includes a fabric envelope within which the ballisticlaminate structure sheets are contained.

An armored garment according to the present invention includes at leastone ballistic panel according to the invention contained within asupporting structure for being worn on a body part.

According to yet another preferred embodiment of the invention, thearmored garment includes a panel for preventing penetration of hand gunrounds, and contains at least 10 and no more than 60 sheets of theballistic laminate structure.

According to yet another preferred embodiment of the invention, thearmored garment includes a panel for preventing penetration of highvelocity rifle rounds containing at least 40 and no more than 150 sheetsof the ballistic laminate structure.

According to yet another preferred embodiment of the invention, thearmored garment includes a fabric envelope within which the ballisticlaminate structure sheets are contained.

An embodiment of the method of fabricating a ballistic laminatestructure in sheet form according to the invention comprises the stepsof forming a first array of high performance, unidirectionally-orientedfiber bundles, forming a second array of high performance,unidirectionally-oriented fiber bundles, and cross-plying the secondarray of fiber bundles at an angle with respect to the first array offiber bundles. Films are bonded to respective opposing outer surfaces ofthe laminated first and second arrays of unidirectional fiber bundleswithout penetration of the films into fiber bundles or through thelaminate from one side of the ballistic laminate structure to the other.

BRIEF DESCRIPTION OF THE DRAWINGS

Some of the objects of the invention have been set forth above. Otherobjects and advantages of the invention will appear as the inventionproceeds when taken in conjunction with the following drawings, inwhich:

FIG. 1 is a simplified flow diagram of the process of fabricating theballistic laminate in sheet form according to a preferred embodiment ofthe invention;

FIG. 2 illustrates formation of the laminate structure from twoidentical laminate sheets;

FIG. 3 further illustrates formation of the laminate structure from twoidentical laminate sheets;

FIG. 4 is an enlarged, diagrammatic representation of the interaction ofthe thin covering films and the unidirectional fiber arrays of thelaminate structure;

FIG. 5 is an enlarged view of a single fiber bundle according to theprior art, showing complete impregnation of the resin into the structureof the fiber bundle;

FIG. 6 is a enlarged view of a single fiber bundle according to anembodiment of the invention showing lack of impregnation of the resininto the structure of the fiber bundle;

FIG. 7 is an armored body garment according to a preferred embodiment ofthe invention;

FIG. 8 is a table showing estimated stopping ability of a prior artaramid (Kevlar) fabric;

FIG. 9 is a table showing estimated stopping ability of a prior artSpectra-Shield polyethylene fabric; and

FIG. 10 is a table showing estimated stopping ability of a aramid fiber(Kevlar) laminate structure according to a preferred embodiment of theinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE

Referring now specifically to the drawings, a ballistic laminatestructure in sheet form according to the present invention isillustrated in FIG. 1 and shown generally at reference numeral 10. Thesheet 10 is created according to the process illustrated in FIG. 1. Aplurality of bundles 11 of untwisted high performance fibers are formedinto an array. The bundles 11 may be supplied from separate creeled yarnpackages 12, as shown in FIG. 1, or may be supplied from a warp beam(not shown). The fibers in the bundles 11 are unidirectional, and thebundles are passed through a comb guide 13 where the fiber bundles 11are further parallelized and formed into an array having a predetermineduniform number of bundles per inch of width. A single layer of fiberbundles 11 are arrayed and then passed over a film application roller 15where a thin polyethylene film 16 is applied to one side of the array offiber bundles 11. A pre-lamination roller 18 presses the array of fiberbundles 11 onto the film 16, which is supported on a heated platen 19.After heating, the fiber bundles and the attached film 16 are laminatedby passing them through a pair of heated nip rolls 20, 21. The assembledlaminate structure is then wound onto a take-up beam 22.

Referring now to FIG. 2, two layers, or plies, of the sheet 10 arebonded to each other with the direction of the fiber bundles at 90degree angles to each other. Other cross ply angles are possible, suchas 45°. The sheets 10 are layered with the respective polyethylene films16 on the outside, so that substantially uncoated high performancefibers are in contact with each other. As is illustrated in FIG. 3, thebonding occurs by further heating of the sheets 10 so that the films 16remelt. The films 16 are extremely thin, on the order of 0.35 mils, sothat the films 16 will slightly coat the exterior surfaces of theindividual fiber bundles 11, but will not penetrate into the fiberbundles 11 so to coat and encapsulate the individual fibers andfilaments. Sufficient plasticized film material 16 flows between theadjacent cross-plied arrays of fiber bundles 11 to bond the two fiberbundles 11 together to form a ballistic laminate structure 25.

As is shown in FIG. 4, the fiber bundles 11 of each of the sheets 10 areat right angles to each other. The outer surface of each of the sheets10 are coated with the film 16. As is illustrated, the film 16 hasmelted and flowed into the interstices between the fiber bundles 11 ofeach of the sheets 10. Sufficient melted polyethylene from both of thefilms 16 have intermingled with each other and coated the outer surfaceof the fiber bundles of the other sheet 10 to create a surface bond withhold the two sheets 10 together to form the laminate structure 25.

This is illustrated more clearly in FIGS. 5 and 6. FIG. 5 shows a priorart construction such as a Spectra-Shield product using both an elasticresin and a surface film. The individual fiber bundles and theindividual fibers which make up the bundle are substantially completelyencapsulated with the elastic resin (the black, surrounding material) aswell as the outside of the fiber bundle. This adds to the weight of theproduct and creates the possibility of variation in quality if too muchor too little resin is used, or if the resin is applied unevenly orinconsistently.

In contrast, the fiber bundles 11 according to the present invention arecoated by the film 16 on the outside surface only, so that the integralstructure of parallel, closely bunched filaments and fibers remainsintact, and intimate contact between the closely bunched filaments andfibers remains. The film 16 may not even coat the entire outer surfaceof the fiber bundle 11, but only to a sufficient degree to properly bondthe two sheets 10 together to form the laminate structure 25. This isalso illustrated in FIG. 4.

A preferred embodiment is given in the following example:

Fiber--Kevlar brand aramid fiber

Fiber construction--840 denier, 1.5 den/fil. per tow.

Sheet Construction--10 ends/inch unidirectional untwisted tows

Number of Sheets in laminate structure--2

Sheet orientation of 1st and 2nd sheets--90 degrees

Film--0.35 mil polyethylene

Laminate structure--intimately plied sheets with overlying,surface-applied polyethylene film

Percentage of fiber weight to film weight--80%

The laminate structure 25 must be used in multiple layers to form aballistic panel for incorporation into a garment. Referring to FIG. 7, aballistic garment 30 is illustrated. The garment 30 incorporates twoprotective ballistic panels. A first panel 31 is formed of multiplelayers of laminate structures 25. A panel 31 for preventing penetrationof conventional rifle rounds contains at least 10 and no more than 40sheets of the ballistic laminate structure 25. A panel 31 for preventingpenetration of hand gun rounds contains at least 40 and no more than 80sheets of the ballistic laminate structure 25. Adequate protection fromextremely high powered rifles or rifles firing steel core and/or steeljacketed rounds may require up to 150 layers. The laminate structures 25are not bound together in any way, but are overlaid in substantialregistration with each other and placed in an envelope or pocket formedin the garment 30.

As is shown in FIG. 7, the panel 31 is relatively large and coverssubstantially the entire thorax region of the wearer. A smaller panel32, which may contain the same, a lesser, or a greater number oflaminate structures 25, is placed over the larger panel 31 in a separatepocket or envelope and provides additional protection to vital organssuch as the heart and lungs. The garment 30 is illustrative of manytypes of garments which can incorporate panels formed of layers of thelaminate structure 25 disclosed in this application.

Referring now to FIG. 8, the graph illustrates that at the 50% predictedprobability level, a standard measure of ballistic efficiency, a priorart fabric constructed of Kevlar 129 fiber will stop a 9 mm round ofammunition traveling at 1400 ft/sec.

Referring to FIG. 9, the graph illustrates that at the 50% predictedprobability level a prior art Spectra Shield fabric will stop a 9 mmround of ammunition traveling at 1450 ft/sec.

In contrast, as is shown in FIG. 10, a Kevlar panel constructed inaccordance with an embodiment of the invention will stop a round of 9 mmammunition traveling at 1500 ft/sec 50 percent of the time. Furthermore,the steeper slope of the graph indicates that at lower velocities, theprobability of the round be stopped by the fabric is further improvedover the prior art. In addition, the lighter weight of the inventivelaminate structure 25, its relative ease of construction and assemblyprovide further advantages.

A high performance fiber laminate structure, ballistic panel, garmentincluding a high performance ballistic panel and a method ofconstructing a high performance fiber laminate structure is describedabove. Various details of the invention may be changed without departingfrom its scope. Furthermore, the foregoing description of the preferredembodiment of the invention and the best mode for practicing theinvention are provided for the purpose of illustration only and not forthe purpose of limitation--the invention being defined by the claims.

I claim:
 1. In a ballistic panel for preventing penetration ofhigh-velocity bullets and fragments through the panel from one side tothe other, the improvement comprising a plurality of ballistic laminatestructure in sheet form assembled together to form the ballistic panel,said laminate structure comprising:(a) a first array of highperformance, unidirectionally-oriented fiber bundles; (b) a second arrayof high performance, unidirectionally-oriented fiber bundles cross-pliedat an angle with respect to said first array of fiber bundles, andlaminated to said first array of fiber bundles in the absence ofadhesives or bonding agents, said first and second arrays of highperformance, unidirectionally-oriented fiber bundles comprising fiberschosen from the group consisting of aramid fiber, ultra high molecularweight polyethylene, high molecular weight polyethylene, high modulusvinylon, and liquid crystal polymer-based fiber; and (c) first andsecond thermoplastic films bonded to outer surfaces of said laminatedfirst and second arrays of unidirectional fiber bundles withoutpenetration of said films into said fiber bundles or through thelaminate structure from one side to the other, whereby a sufficientamount of film resides between the laminated first and second arrays ofunidirectional fiber bundles to adhere the first and second arrays offiber bundles together to form the ballistic laminate structure.
 2. Animproved ballistic panel according to claim 1, wherein the first arrayof fiber bundles is cross-plied at an angle of 90 degrees to the secondarray of fiber bundles.
 3. An improved ballistic panel according toclaim 1, wherein said first and second thermoplastic films comprisepolyethylene film having a thickness of 0.35 mils.
 4. An improvedballistic panel according to claim 1, wherein the percentage by weightof the high performance fibers in the ballistic laminate structure is atleast 80 percent of the total weight of the ballistic laminatestructure.
 5. An improved ballistic panel according to claim 1, andcomprising at least 10 and no more than 60 sheets of the ballisticlaminate structure for preventing penetration of hand gun rounds.
 6. Animproved ballistic panel according to claim 1, and comprising at least40 and no more than 150 sheets of the ballistic laminate structure forpreventing penetration of high velocity rifle rounds.
 7. An improvedballistic panel according to claim 1, and including a fabric envelopewithin which the ballistic laminate structure sheets are contained. 8.In a ballistic panel for preventing penetration of high-velocity bulletsand fragments through the panel from one side to the other, theimprovement comprising a plurality of ballistic laminate structure insheet form assembled together and contained in a fabric envelope to formthe ballistic panel, said laminate structure comprising:(a) a firstarray of high performance, unidirectionally-oriented aramid fiberbundles; (b) a second array of high performance,unidirectionally-oriented aramid fiber bundles cross-plied at an angleof 90 degrees with respect to said first array of fiber bundles, andlaminated to said first array of fiber bundles in the absence ofadhesives or bonding agents, said first and second arrays of highperformance, unidirectionally-oriented fiber bundles comprising fiberschosen from the group consisting of aramid fiber, ultra high molecularweight polyethylene, high molecular weight polyethylene, high modulusvinylon, and liquid crystal polymer-based fiber; and (c) first andsecond thermoplastic films bonded to outer surfaces of said laminatedfirst and second arrays of unidirectional fiber bundles withoutpenetration of said films into said fiber bundles or through thelaminate structure from one side to the other, whereby a sufficientamount of film resides between the laminated first and second arrays ofunidirectional fiber bundles to adhere the first and second arrays offiber bundles together to form the ballistic laminate structure.
 9. Animproved ballistic panel according to claim 8, wherein said first andsecond thermoplastic films comprise polyethylene film having a thicknessof 0.35 mils.
 10. An improved ballistic panel according to claim 8,wherein the percentage by weight of the high performance fibers in theballistic laminate structure is at least 80 percent of the total weightof the ballistic laminate structure.
 11. An improved ballistic panelaccording to claim 8, and comprising at least 10 and no more than 60sheets of the ballistic laminate structure for preventing penetration ofhand gun rounds.
 12. An improved ballistic panel according to claim 8,and comprising at least 40 and no more than 150 sheets of the ballisticlaminate structure for preventing penetration of high velocity riflerounds.